I'm having a dickens of a time trying to get one of my SBC's clean.

I think I did a pretty good job soldering it together. However, I guess I waited too long to clean the board or something. I didn't use any flux because it was just a bunch of through-hole pins. Maybe that was my mistake.

Anyway, the bottom of the board is tacky and the solder joints now look tarnished instead of the shiny silver they were just a few months ago.

I scrub and scrub with 99% IPA and a toothbrush but after the IPA evaporates, the board almost seems worse!

So I decided to scrub with warm water and dish detergent and rinse heavily with distilled water. No dice. Still dingy. (PS, I've had success with this in the past with other boards)

Next, I literally let the board soak in a small bath of IPA for a few hours. This helped with the tacky feeling of the board but not completely.

I guess I could re-touch each pin and reflow the solder to get back that shine.

What am I doing wrong? I'm using lead-free solder, a good iron and my solder joints look really good. Other than turning gray.

I've seen a million videos where the person just swabs some IPA after soldering and their boards look clean. I do it, and it looks clean but in a short amount of time, it gets sticky, dingy and even flaky around the solder joints.

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Cat; the other white meat.

I use special flux remover, works much better than alcohol.

Did the solder have a flux core? That would be a source of flux.

I can't remember at the moment. I will have to look when I get home.

It was whatever kind Dave recommended over at the EEVBlog.

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Cat; the other white meat.

Soldering without flux (internal or external) is almost impossible. You get very rapid oxidation, and the oxides prevent flow and wetting, and make a brittle mess.

Boy, that sounds like a waste of perfectly good beer...

You're assuming I didn't drink it afterwards.

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Cat; the other white meat.

Beside flux remains (IPA could get rid of that, but slowly) what might cause your solder joints to look ugly is silver sulfide (AgS). Some lead-free solder have pretty much silver inside. Perhaps you try cleaning your board with some drops of a silver (dip) bath. If that helps - it would help only shortly. You would need to use some sort of coat to prevent re-tarnishing.

It kind of sounds like the flux in your solder was not rosin. Rosin-core solder won't make things dingy and dull. You can leave the rosin on there for years, then chip it off, and the surface of the solder will be bright and shiny. This flux doesn't hurt anything. You can just leave it indefinitely; but if you want the board looking clean, wait until it's cool so the rosin flux is hard, then chip most of it off gently with a dull X-Acto knife (dull so you don't scratch the board, which is counterproductive to good looks), then take a Q-Tip moistened (not dripping) with acetone to clean up the little that's left. [Disclaimer: I've never used lead-free solder, and I hope to never have to. The company I work for has basically told the European market that they're more trouble than they're worth.]

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

I don't know what all of the numbers mean, but the label on my solder says:

"FLUX 2.0% 63%"
"DIA 0.6mm 1000g"

That's it. I'm assuming 2% flux core and 63% of some metal like tin?

The brand is "Solder Wire" and some Chinese characters.

So who knows what kind of quality it has. I think I might try and find some older boards I've done with this stuff and see what they are looking like.

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Cat; the other white meat.

I use 3 different types of solder depending on the type or work I'm doing, but all are rosin activated. For standard PCB work (like my 65C02 projects), I use standard 60/40 in 0.032" diameter, 3% RA.

https://www.mouser.com/ProductDetail/AI ... XiaWCGk%3d

For defluxing the board, I use Techspray G3:

https://www.mouser.com/ProductDetail/Te ... ibGPio%2fL

I've never had any issues with PCBs being sticky or getting dingy, even after 5+ years.

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Regards, KM
https://github.com/floobydust

Thanks. I added those to my project list at Mouser.

This morning I dug out an old board I did about 2-3 years ago. I specifically remember having the same issue back then. I also remember soaking the board in 99% IPA for several hours and scrubbing the hell out of it with a firm brush.

Today, the board is super shiny with the exception of the solder joints. They look dull and gray. I know for a fact it's from the same solder I have now.

Maybe I should replace this solder with something better?

Funny thing is, I still have a LOT of it left. Even though I do a lot of soldering.


**EDIT**

As a side question...I have heard/read many MANY times that lead is ideal for solder because it's easier to work with. So, how do you guys deal with the toxicity of it? I have a fume extractor that I (mostly) use. But what else can I do to prevent anything bad from happening?

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Cat; the other white meat.

There are generally no issues from lead solder when working with it.

Molten lead is fine unless you drop it onto yourself, just don't boil it and start inhaling the fumes.

And don't lick the PCBs you've just soldered up with it - even then, you're at more risk of cutting your tongue and toxicity from the flux.

The fumes are flux fumes - and those - well yes,you might not want to breathe them for long, so the usual well-ventilated workspace is fine for hobbyist use and remember to wash your hands afterwards.

The whole lead-free thing is generally about what goes into landfill and the (real) risk of lead leaching out into watercourses or being boiled away in an incinerator, or carried as dust out of a crusher.

Leaded solder is perfectly fine for hobbyist use, even here in the UK where commercial stuff has to be lead-free now, so use (60:40) leaded solder for stuff you make and read-up on the local rules & regs for stuff you sell.

I've used "Ersin 60/40 multicore" 0.7mm solder for virtually everything I've done now - probably in the past 40+ years. I was given a small roll back then and just kept buying more when I needed it. Once I get a good thing, I tend to stick with it...

-Gordon

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--
Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/

This means you have a flux-core (probably rosin) solder wire using the eutectic 63/37 tin-lead alloy. This is one of the standard solders for electronics work; another common type is 60/40 tin-lead which is still near-eutectic. The 0.6mm refers to the nominal diameter of the wire (which is non-critical), and 1000g refers to the total quantity supplied on the reel (potentially enough to last an occasional hobbyist for a lifetime).

Eutectic alloys refer to ratios of composition in which the entire alloy melts and freezes at the same temperature, which will be the lowest melting point of any ratio of the same component metals. Near-eutectic alloys will have a small temperature range over which melting and freezing occurs, so there'll be a couple of seconds of "plastic" phase as the joint cools. Plumber's solders often have a greater deviation from the eutectic ratio, so that the joint can be "wiped" during cooling to help seal it. For electronics work, the eutectic alloy should be fine.

Lead-free solders were first introduced for jewellery and plumbing work (since you don't want even traces of lead in your drinking water), and more recently for lead-free electronics. Their melting points tend to be somewhat higher than tin-lead solders, which makes them more difficult to work with as hobbyists - especially if you have a "dumb" iron without temperature control. As noted, they're mainly of concern for large-scale commercial production.

So there's probably nothing wrong with your solder, provided it is as described - and there's no real reason why it wouldn't be.